The present invention relates to an image pickup apparatus for producing a video signal from an optical image by driving a solid imaging device and by performing video-signal processing, according to a plurality of scanning systems including a progressive-scanning system.
A conventional image pickup apparatus of progressive-scanning type has structure, for example, as shown by the block diagram of FIG. 11. The conventional image pickup apparatus of FIG. 11 comprises a charge coupled device (CCD) imaging device 1 that is a solid imaging device of a progressive-scanning type, an imaging device driving circuit (hereinafter referred to as CCD driving circuit) 2 for driving the CCD imaging device 1, a preamplifier 3 for obtaining a good video signal in regard to signal-to-noise (SN) ratio from the output signal of the CCD imaging device 1, an analog-to-digital (A/D) converter 4 for converting the output signal of the amplifier 3 to a digital signal, a digital processing circuit 5a for providing various video-signal processing on the digital signal, a video tape recorder interface (VTR I/F) circuit 6 for converting the output signal of the digital processing circuit 5a to a signal that can be recorded by a VTR 7 that records a progressive-scanning signal, and a progressive-scanning synchronizing signal producing circuit 8 for supplying a progressive-scanning synchronizing signal, by which the output signals of all of the above composing members are synchronized.
The following is description on the operation of the conventional image pickup apparatus. The output signal of the CCD imaging device 1 is produced by performing progressive-scanning on the CCD imaging device 1 according to the progressive-scanning synchronizing signal. The low frequency noise that is included in the output signal of the CCD imaging device 1 is decreased by the preamplifier 3 comprising a correlated-double-sampling circuit. The output signal of the preamplifier 3 is converted to a digital signal by the A/D converter 4, and undergoes various video-signal processing such as gamma correction, enhancement, matrix processing, and the like in the digital processing circuit 5a. The output signal of the digital processing circuit 5a is converted by the VTR I/F circuit 6 to the signal that can be recorded by the VTR 7. In more detail, the VTR 7 records the progressive-scanning video signal of the studio standard of the 525/60P mode, which has 525 horizontal lines, 33.5 kHz horizontal frequency, and 59.94 Hz vertical frequency.
In the above structure, if the frequencies of the synchronizing signals supplied to all composing members including the CCD imaging device is changed to half, the progressive-scanning signal of the 525 horizontal lines, 15.75 kHz horizontal frequency and 29.97 Hz vertical frequency (hereinafter referred to as a 525/30P mode) can be obtained. An image pickup apparatus that is usable for the two modes of the 525/60P mode and the 525/30P mode can be thus obtained.
However, in the image pickup apparatus used for both 525/60P mode and 525/30P mode, the circuits of all composing members are to be operable for the two different modes, which result in extreme difficulty in optimizing the CCD imaging device 1 and the preamplifier 3. In more detail, the frequencies of two horizontal driving pulses having respectively different phases for reading out by transferring horizontally the signal-electric-charge (hereinafter referred to as signal-charge) that is charged in the CCD imaging device 1 and the frequency of the reset-pulse at the output portion of the CCD imaging device 1 are, in general, as high as 30-50 MHz in the 525/60P mode and 15-25 MHz in the 525/30P mode, though these frequencies are different depending on the number of pixels of the CCD imaging device 1. Therefore, it is extremely difficult to adjust optimally, for the two different modes, the phase positioning and the waveforms of the above three pulses, which are the factors of determining the performance such as sensitivity, frequency characteristics and the like of the CCD imaging device 1.
Also, the preamplifier 3 produces a good video signal in regard to SN ratio from the output signal of the CCD imaging device 1 by decreasing the low frequency noise of the output signal in such a manner that the output signal is sampled by using two pulses having respectively different phases, and the difference between the waveforms of the two signal samples, which is a noise component, is eliminated, in which, the phase positioning and the waveforms of the two pulses for the signal sampling are the factors of determining the degree of the improvement of the signal quality in regard to the SN ratio, as in the case of the above CCD driving pulses. In this case also, it is extremely difficult to adjust optimally the phase positioning and the waveforms of the two pulses for the above two different modes, which also makes the circuit complicated.
In addition, for decreasing the influence of the pulses for driving the CCD imaging device 1 and for signal sampling for noise reduction in the preamplifier 3, filters for intercepting these pulses are used in analog-processing of pre-processing before introducing the signal into the A/D converter 4. In this case also, since the filters for the above two different modes are needed, the circuit becomes complicated.
The present invention is to address the above problems, i.e., the present invention aims to provide an image pickup apparatus that has a simple circuit and good performance for the use in the two modes of the 525/60P mode and the 525/30P mode, or three modes including one more the 525i mode of interlaced-scanning.
An image pickup apparatus of the present invention, for realizing the above aim, comprises a signal-charge reading-control circuit for switching either to mode-1 in which one pulse is supplied in each vertical scanning interval (hereinafter referred to as a field) of progressive scanning, or to mode-2 in which one pulse is supplied in every two fields of progressive scanning, for reading out the signal-charge that is charged in a CCD imaging device as the output signal of the CCD imaging device, a writing-control circuit that works for writing, into a memory, the output signal of the CCD imaging device, during the intervals when the output signal is obtained by reading out the signal-charge that is charged in the CCD imaging device, and, a reading-control circuit that works for reading out, in the mode-1, the signal written in the memory according to a progressive-scanning synchronizing signal, and for reading out, in the mode-2, the signal written in the memory according to an interlaced-scanning synchronizing signal in such a manner that odd scanning lines (hereinafter referred to as xe2x80x9clinexe2x80x9d for xe2x80x9cscanning linexe2x80x9d) are read out in each odd field and even lines are read out in each even field. The above structure enables the image pickup apparatus to have a simple circuit and good performance for the use in the two modes of the 525/60P mode and the 525/30P mode. More details are described hereinafter.
A first invention of the present invention is that the image pickup apparatus comprises a CCD imaging device, a progressive-scanning synchronizing signal producing circuit for supplying a progressive-scanning synchronizing signal, an interlaced-scanning synchronizing signal producing circuit for supplying an interlaced-scanning synchronizing signal having a vertical synchronizing signal of the frequency that is identical with the frequency of the vertical synchronizing signal of the progressive-scanning synchronizing signal, and a horizontal synchronizing signal of the frequency that is substantially the half of the frequency of the horizontal synchronizing signal of the progressive-scanning synchronizing signal, an imaging-device driving circuit for supplying a driving signal for performing scanning on the CCD imaging device according to the progressive-scanning synchronizing signal, a signal-charge reading-control circuit for switching either to mode-1 in which one reading pulse, which is included in the driving signal supplied by the imaging-device driving circuit, is supplied in each field of progressive-scanning, or to mode-2 in which one reading pulse is supplied in every two fields of progressive scanning, for reading out signal-charge that is charged in the CCD imaging device as the output signal of the CCD imaging device, a memory into which the output signal of the CCD imaging device is written, a writing-control circuit that works for writing, into the memory, the output signal of the CCD imaging device, during the intervals when the output signal is obtained by reading out the signal-charge that is charged in the CCD imaging device, and, a reading-control circuit that works for reading out, in the mode-1, the signal written in the memory according to the progressive-scanning synchronizing signal, and for reading out, in the mode-2, the signal written in the memory in such a manner that odd lines are read out in each odd field and even lines are read out in each even field according to the interlaced-scanning synchronizing signal.
From the above structure, in the mode-1, the signal of the 525/60P mode can be obtained according to the progressive-scanning synchronizing signal.
And, in the mode-2, the signal of the 525/30P mode, which is virtually identical with the signal of the 525i mode, can be obtained in such a manner that a field in which the signal-charge is read out, and another field in which the signal-charge is not read out are alternately repeated (the signal is a progressive-scanning signal obtained in every {fraction (1/30)} second), then, the signal thus obtained from the CCD imaging device is written into the memory once in every two fields, i.e. the signal is written into the memory during the intervals when the output signal of the CCD imaging device is obtained by reading out the signal-charge that is charged in the CCD imaging device, then, the signal written in the memory is read out in such a manner that odd lines are read out in each odd field, and even lines are read out in each even field. From the above structure, an image pickup apparatus, which has a simple circuit, good performance, and is usable for the two modes of the 525/60P mode and the 525/30P mode can be obtained.
A second invention of the present invention is that a recording unit (hereinafter referred to as a VTR) that can record the signal of the 525/60P mode or the 525i mode is added to the above first invention. As a result, the VTR can record the signal of the 525/60P mode in the mode-1, or the signal of the 525/30P mode in the mode-2.
A third invention of the present invention is that a P/I (progressive/interlaced-scanning) converting circuit is added to the above first invention. The P/I converting circuit produces an interlaced-scanning signal of the 525i mode by adding two lines of the signal of the 525/60P mode, which is read out from the memory in the mode-1, alternately decimating the added lines, and expanding the time base of the signal comprising the added lines to double. The above structure realizes the image pickup apparatus that is usable for the three modes of the 525/60P mode, the 525/30P mode, and the 525i mode.
A fourth invention of the present invention is that the VTR that can record the signal of the 525/60P mode or the 525i mode is added to the above third invention. As a result, the VTR can record the signal of the 525/60P mode when the VTR is in the 525/60P mode, or, the signal of the 525/30P mode or the 525i mode when the VTR is in the 525i mode.
A fifth invention of the present invention is that the image pickup apparatus comprises a progressive-scanning synchronizing signal producing circuit for supplying a progressive-scanning synchronizing signal, an interlaced-scanning synchronizing signal producing circuit for supplying an interlaced-scanning synchronizing signal having the vertical synchronizing signal of the frequency that is identical with the frequency of the vertical synchronizing signal of the progressive-scanning synchronizing signal, and the horizontal synchronizing signal of the frequency that is substantially the half of the frequency of the horizontal synchronizing signal of the progressive-scanning synchronizing signal, a CCD imaging device that is composed in such a manner that scanning is performed on the CCD imaging device according to the progressive-scanning synchronizing signal, and that all odd lines are read out in the first half of each field and all even lines are read out in the latter half of each field, or all even lines are read out in the first half of each field and all odd lines are read out in the latter half of each field, an imaging-device driving circuit for supplying a driving signal that performs scanning on the CCD imaging device according to the progressive-scanning synchronizing signal, a signal-charge reading-control circuit for switching either to mode-1 in which one reading pulse, which is included in the driving signal, is supplied in each field of progressive scanning, or to mode-2 in which one reading pulse is supplied in every two fields of progressive scanning, for reading out the signal-charge that is charged in the CCD imaging device, a memory into which the output signal of the CCD imaging device is written, a writing-control circuit that works for writing, into the memory, the output signal of the CCD imaging device, during the intervals when the output signal is obtained by reading out the signal-charge that is charged in the CCD imaging device, and, a reading-control circuit that works for reading out the signal written in the memory according to the interlaced-scanning synchronizing signal in the form of two separate interlaced-scanning signals in the mode-1, or in the form of one interlaced-scanning signal in the mode-2.
From the above structure, the signal of the 525/60P mode comprising two separate signals can be produced by utilizing the two separate interlaced-scanning signals that are obtained in the mode-1, or, the signal of the 525/30i mode can be produced by utilizing one interlaced-scanning signal that is obtained the mode-2.
A sixth invention of the present invention is that the VTR is disposed in place of the digital output circuits in the above fifth invention. The VTR can record the signal of the 525/60P mode in the mode-1 by recording the two separate interlaced-scanning signals, or the signal of the 525/30i mode in the mode-2 by recording one interlaced-scanning signal. As a result, the VTR can record the signal of the 525/60P mode in the mode-1, or the signal of the 525/30P mode in the mode-2.
A seventh invention of the present invention is that a P/I converting circuit is added to the above fifth invention. The P/I converting circuit produces the signal of the 525i mode by adding two corresponding lines of the two separate interlaced-scanning signals that are read out from the memory in the mode-1. As a result, an image pickup apparatus that is usable for the three modes of the 525/60P mode, the 525/30P mode and the 525i mode can be obtained.
A eighth invention of the present invention is that the VTR that can record the signal of the 525/60P mode or the 525i mode is added to the above seventh invention. As a result, the VTR can record the signal of the 525/60P mode when the VTR is in the 525/60P mode, or, the signal of the 525/30P mode or the 525i mode when the VTR is in the 525i mode. In other words, the VTR records two interlaced-scanning signals in the mode-1, one interlaced-scanning signal in the mode-2, or the output signal of the P/I converting circuit.